The use of steam coagulation processes for finishing random and block copolymers is described in European patent application no. 0413403. Said European patent application, and in particular page 6, lines 7, 8, and lines 54-56, teaches treating a cement of random copolymers or block copolymers from monovinyl aromatic and conjugated diene and a solvent, comprising for a significant part cyclopentane, after termination of the organo alkali metal initiated anionic polymerization reaction of predominantly monovinyl aromatic and predominantly conjugated diene by means of either a proton donating agent in the case of a fully sequentially prepared block copolymer or a coupling agent in the case of an initially prepared intermediate diblock copolymer, by means of steam coagulation.
However, a generally appreciated shortcoming of such a process, in particular when applied on block copolymers derived from monovinyl aromatic hydrocarbons and conjugated dienes and having a relative low viscosity, was the formation of large agglomerates and severe rector fouling and/or the finishing of said block copolymers proceeding in very low throughputs, and therefore additional recovery costs. On the other hand, it was generally known to the average person skilled in the art that alternative finishing methods involved with much higher capital investments due to additional expensive equipment.
The need for block copolymers derived from predominantly monovinyl aromatic and predominantly conjugated diene having a relatively low viscosity, for several modern block copolymer end use applications, e.g. pressure sensitive adhesives, was still growing. On the other hand, the economy of block copolymer finishing was demanding lower costs, i.e. higher throughputs, reduced clean out time due to avoid or diminish fouling, and lower capex.
An object of the present invention was therefore to provide an improved process for the coagulation finishing of (co)polymers, and in particular those derived from predominantly conjugated diene and/or predominantly monovinyl aromatic hydrocarbons.
It will be appreciated that with the term "process for coagulation finishing of (co) polymers," as used throughout the present specification, is meant to cover in principal all finishing processes wherein a (co)polymer containing organic solvent solution is mixed with an immiscible liquid, wherein the polymer is substantially not soluble, under simultaneous supply of heat to devolatilize a substantial part of the organic solvent by means of a hot fluid, such as steam or a hot inert gas e.g. nitrogen. Of these embodiments the steam coagulation finishing process is the most preferred. As a result of extensive research and experimentation such an improved process aimed at has surprisingly been found.